diff --git a/.github/workflows/versions-matrix/action.R b/.github/workflows/versions-matrix/action.R
index 2283637..b2b94c9 100644
--- a/.github/workflows/versions-matrix/action.R
+++ b/.github/workflows/versions-matrix/action.R
@@ -1,4 +1,56 @@
-json <- '{"include":[{"os": "macos-latest", "r": "release"}, {"os": "ubuntu-20.04", "r": "release"}, {"os": "ubuntu-22.04", "r": "devel", "http-user-agent": "release"}]}'
+# - {os: macos-latest,   r: 'release'}
+#
+# - {os: ubuntu-20.04,   r: 'release'}
+#
+# # Use older ubuntu to maximise backward compatibility
+# - {os: ubuntu-22.04,   r: 'devel',     http-user-agent: 'release'}
+# - {os: ubuntu-22.04,   r: 'release',   covr: true,                  desc: 'with covr'}
+# - {os: ubuntu-22.04,   r: 'oldrel-1'}
+#
+# # Begin custom: R 3.6
+# - {os: ubuntu-22.04,   r: 'oldrel-2'}
+# # End custom: R 3.6
+#
+# # Begin custom: R 3.5
+# - {os: ubuntu-22.04,   r: 'oldrel-3'}
+# # End custom: R 3.5
+#
+# # Begin custom: R 3.4
+# - {os: ubuntu-22.04,   r: 'oldrel-4'}
+# # End custom: R 3.4
+
+# FIXME: Dynamic lookup by parsing https://svn.r-project.org/R/tags/
+r_versions <- c("devel", paste0("4.", 4:0))
+macos <- data.frame(os = "macos-latest", r = r_versions[2:3])
+windows <- data.frame(os = "windows-latest", r = r_versions[1:3])
+linux_devel <- data.frame(os = "ubuntu-22.04", r = r_versions[1], `http-user-agent` = "release", check.names = FALSE)
+linux <- data.frame(os = "ubuntu-22.04", r = r_versions[-1])
+covr <- data.frame(os = "ubuntu-22.04", r = r_versions[2], covr = "true", desc = "with covr")
+
+include_list <- list(macos, windows, linux_devel, linux, covr)
+print(include_list)
+
+filter <- read.dcf("DESCRIPTION")[1,]["Config/gha/filter"]
+if (!is.na(filter)) {
+  filter_expr <- parse(text = filter)[[1]]
+  subset_fun_expr <- bquote(function(x) subset(x, .(filter_expr)))
+  subset_fun <- eval(subset_fun_expr)
+  include_list <- lapply(include_list, subset_fun)
+  print(include_list)
+}
+
+to_json <- function(x) {
+  if (nrow(x) == 0) return(character())
+  parallel <- vector("list", length(x))
+  for (i in seq_along(x)) {
+    parallel[[i]] <- paste0('"', names(x)[[i]], '":"', x[[i]], '"')
+  }
+  paste0("{", do.call(paste, c(parallel, sep = ",")), "}")
+}
+
+configs <- unlist(lapply(include_list, to_json))
+json <- paste0('{"include":[', paste(configs, collapse = ","), ']}')
+
 if (Sys.getenv("GITHUB_OUTPUT") != "") {
   writeLines(paste0("matrix=", json), Sys.getenv("GITHUB_OUTPUT"))
 }
diff --git a/DESCRIPTION b/DESCRIPTION
index 658de92..8dec641 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -29,3 +29,4 @@ Config/testthat/edition: 3
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.3.1
+Config/gha/filter: os != "windows-latest"